<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      var person = {
        age: 18,
        sex: 'boy',
      };
      // person.hobby = 'eat';
      // person.sex = 'girl';
      // delete person.age;
      // console.log(person.age);
      person['hobby'] = 'eat';

      console.log(person['sex']);
    </script>
  </body>
</html>
